Field of the Invention
The present invention relates to an image pickup apparatus configured to pick up an image of an eye to be inspected and a method of controlling the image pickup apparatus.
Description of the Related Art
At present, various ophthalmic image pickup apparatus are used that are configured to scan an eye to be inspected with measuring light and to make an observation and pick up an image using the scanning light that is reflected by the eye to be inspected. Exemplary ophthalmic apparatus include an optical coherence tomography (OCT) system, a scanning laser ophthalmoscope (SLO), and an adaptive optics scanning laser ophthalmoscope (AO-SLO). Those apparatus employ a technology in which a galvano scanner, a resonant scanner, a polygon scanner, or the like is used to scan an eye to be inspected with measuring light so that data at a plurality of points of the eye to be inspected are continuously acquired.
When this technology is used, in order to correctly observe or pick up an image of a desired part of the eye to be inspected, it is necessary to accurately detect a scanning speed and a scanning position of the measuring light on the eye to be inspected in the ophthalmic apparatus. However, it is known that the scanning speed and the scanning position of a scanner used in the ophthalmic image pickup apparatus vary depending on various factors such as individual differences and ambient temperature change.
As a solution to the problem, a technology is known in which a correcting chart is attached at a position conjugate to a light receiving element, and timing of sampling for acquiring a signal from the reflected light is corrected through comparison between a picked-up image of the correcting chart and an image of a fundus (Japanese Patent Application Laid-Open No. 2014-68704). Further, a technology is known in which timing of the sampling is corrected based on a position signal acquired from a drive portion of a resonant scanner (Japanese Patent Application Laid-Open No. 2014-68703).
However, in Japanese Patent Application Laid-Open No. 2014-68704, there is no disclosure of a specific position at which the correcting chart is arranged, and when the correcting chart is attached within an optical axis of an image pickup optical system, it is necessary to attach a new correcting chart every time the data for correction is updated. In this case, there is a problem in that update of the data for correction takes time. In particular, when the scanning speed or the scanning position changes during inspection of an eye and update of the data for correction is attempted for the purpose of identifying the reason for the change, it is often difficult for a user to attach a new correcting chart during the inspection.
Further, the method exemplified in Japanese Patent Application Laid-Open No. 2014-68703 in which a position signal acquired from the drive portion of the resonant scanner is used cannot be applied to a scanner that cannot acquire a position signal. Further, the position signal indicates the position of the scanner alone, and thus, shift of the position of an entire scanner unit in the ophthalmic image pickup apparatus cannot be corrected. In other words, the scanning speed and the scanning position of the measuring light in the ophthalmic image pickup apparatus cannot be accurately corrected.